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Abstract:

Embodiments of systems and methods are presented to provide local
citizenry with the ability to initiate emergency calls on their mobile
device through a deployable cellular communication resource, such as a
switch on wheels. The mobile device may be provisioned with a primary
preferred roaming list (PRL) and a secondary PRL. The secondary PRL is
accessed only when a switch-to-secondary-PRL flag is set in the primary
PRL. Upon detection of the switch-to-secondary-PRL flag, the mobile
device may enter an emergency call mode which only allows the mobile
device to initiate an emergency call. If no network listed in the primary
PRL and no emergency network listed in the secondary PRL is available,
the mobile device may pause for a predetermined time before repeating
attempts to access a network in order to conserver battery power until
cellular communication networks are repaired or temporary networks
implemented.

Claims:

1. A method for providing emergency call service access to a deployable
wireless network resource, comprising:provisioning a mobile device with a
primary preferred roaming list (PRL) and a secondary PRL, wherein the
primary PRL lists communication networks to which the mobile device is
permitted full access and wherein the secondary PRL lists communication
networks to which the mobile device is permitted limited emergency call
access;detecting a switch-to-secondary-PRL flag included within the
primary PRL while attempting to access communication networks listed in
the primary PRL;switch-to-secondary-PRL flag selecting an emergency
communication network from the secondary PRL upon detection of the
switch-to-secondary-PRL flag;scanning a frequency listed in the secondary
PRL for the selected emergency communication network;receiving a system
identification number (SID) on the scanned frequency;comparing the
received SID to an SID of the selected emergency communication network
listed in the secondary PRL; andallowing emergency call initiation on the
mobile device if the received SID matches the SID of the selected
emergency communication network.

2. The method of claim 1, further comprising updating
switch-to-secondary-PRL flag the primary and secondary PRL to set the
switch-to-secondary-PRL flag.

3. The method of claim 2, wherein the primary and secondary PRL are
updated over the air in advance of a predicted weather event to mobile
devices in a region predicted to be affected by the weather event.

4. The method of claim 1, further comprising allowing the mobile device to
receive calls from emergency service personnel if the received SID
matches the SID of the selected emergency communication network.

5. The method of claim 1, further comprising allowing the mobile device to
receive SMS from emergency service personnel if the received SID matches
the SID of the selected emergency communication network.

6. The method of claim 1, further comprising placing the mobile device in
a standby mode for a predetermined period of time if the received SID
does not match the SID of the selected emergency communication network.

7. A mobile device, comprising:a processor;a wireless transceiver coupled
to the processor; anda memory coupled to the processor,wherein the memory
has stored therein provisioning information including a primary preferred
roaming list (PRL) and a secondary PRL, the primary PRL listing
communication networks to which the mobile device is permitted full
access and the secondary PRL listing communication networks to which the
mobile device is permitted limited emergency call access, andwherein the
processor is configured with executable software instructions to perform
steps comprising:detecting a switch-to-secondary-PRL flag included within
the primary PRL while attempting to access communication networks listed
in the primary PRL;selecting an emergency communication network from the
secondary PRL upon detection of the switch-to-secondary-PRL
flag;attempting to access the selected emergency communication network
using a frequency listed in the secondary PRL;receiving a system
identification number (SID) on the frequency listed in the secondary
PRL;comparing the received SID to an SID of the selected emergency
communication network listed in the secondary PRL; andallowing emergency
call initiation on the mobile device if the received SID matches the SID
of the selected emergency communication network.

8. The mobile device according to claim 7, wherein the processor is
configured with executable software instructions to perform further steps
comprising receiving an update to the primary and secondary PRL.

9. The mobile device according to claim 7, wherein the processor is
configured with executable software instructions to perform further steps
comprising receiving an update to the primary PRL which sets a
switch-to-secondary-PRL flag stored within at least one record within the
primary PRL.

10. The mobile device according to claim 7, wherein the processor is
configured with executable software instructions to perform further steps
comprising completing a call to the selected emergency communication
network only if a dialed number is for a recognized emergency service.

11. The mobile device according to claim 10, wherein number for a
recognized emergency service is 911.

12. The mobile device according to claim 7, wherein the processor is
configured with executable software instructions to perform further steps
comprising monitoring the selected emergency communication network for
simple message service (SMS) messages.

13. The mobile device according to claim 10, further comprising a global
positioning system (GPS) receiver coupled to the processors, wherein the
processor is configured with executable software instructions to perform
further steps comprising:determining location coordinates of the mobile
device using the GPS receiver; andincluding the location coordinates in
communications with the selected emergency communication network when
completing the call to the recognized emergency service.

14. The mobile device according to claim 7, wherein the processor is
configured with executable software instructions to perform further steps
comprising selecting another emergency communication network from the
secondary PRL if no pilot signal is received in the attempt to access the
selected emergency communication network using a frequency listed in the
secondary PRL or the received SID does not match the SID of the selected
emergency communication network.

15. The mobile device according to claim 14, wherein the processor is
configured with executable software instructions to perform further steps
comprising pausing for a predetermined period of time before searching
for a new communication network if communication could not be establish
with any emergency communication network listed in the secondary PRL.

16. A tangible storage medium having stored therein processor-executable
software instructions configured to cause a mobile device processor to
perform steps comprising:detecting a switch-to-secondary-PRL flag
included within a primary preferred roaming list (PRL) while attempting
to access communication networks listed in the primary PRL;selecting an
emergency communication network from a secondary PRL upon detection of
the switch-to-secondary-PRL flag;attempting to access the selected
emergency communication network using a frequency listed in the secondary
PRL;receiving a system identification number (SID) on the frequency
listed in the secondary PRL;comparing the received SID to an SID of the
selected emergency communication network listed in the secondary PRL;
andallowing emergency call initiation on the mobile device if the
received SID matches the SID of the selected emergency communication
network.

17. The tangible storage medium of claim 16, wherein the therein
processor-executable software instructions stored therein are configured
to cause a mobile device processor to perform further steps comprising
receiving an update to the primary and secondary PRL.

18. The tangible storage medium of claim 16, wherein the therein
processor-executable software instructions stored therein are configured
to cause a mobile device processor to perform further steps comprising
receiving an update to the primary PRL which sets a
switch-to-secondary-PRL flag stored within at least one record within the
primary PRL.

19. The tangible storage medium of claim 16, wherein the therein
processor-executable software instructions stored therein are configured
to cause a mobile device processor to perform further steps comprising
completing a call to the selected emergency communication network only if
a dialed number is for a recognized emergency service.

21. The tangible storage medium of claim 16, wherein the therein
processor-executable software instructions stored therein are configured
to cause a mobile device processor to perform further steps
comprising:determining location coordinates of the mobile device using a
GPS receiver; andincluding the location coordinates in communications
with the selected emergency communication network when completing the
call to the recognized emergency service.

22. The tangible storage medium of claim 16, wherein the
processor-executable software instructions stored therein are configured
to cause a mobile device processor to perform further steps comprising
selecting another emergency communication network from the secondary PRL
if no pilot signal is received in the attempt to access the selected
emergency communication network using a frequency listed in the secondary
PRL or the received SID does not match the SID of the selected emergency
communication network.

23. The tangible storage medium of claim 16, wherein the
processor-executable software instructions stored therein are configured
to cause a mobile device processor to perform further steps comprising
pausing for a predetermined period of time before searching for a new
communication network if communication could not be establish with any
emergency communication network listed in the secondary PRL.

Description:

RELATED APPLICATIONS

[0001]This application claims the benefit of priority to U.S. Provisional
Patent Application No. 61/045,588 entitled "Method and System for
Providing a Deployable Emergency Call Service for Wireless Handsets"
filed Apr. 16, 2008, the entire contents of which are hereby incorporated
by reference.

FIELD OF THE INVENTION

[0002]The present invention relates generally to a wireless mobile
communication system, and more particularly to methods and systems which
provides wireless mobile devices access to a deployable emergency call
service.

BACKGROUND

[0003]Emergency services such as police and fire rescue often rely upon
the local citizenry to alert emergency services of emergency situations.
In order to do so, nearly every community in the United States has
implemented an emergency call service, such as the well known 911
service. To be effective, an emergency call service needs to accomplish
three goals. First, the emergency call service should recognize when
someone dials the emergency number on any phone (even a pay phone when no
coins have been supplied). Second, the emergency call service should
route the call to the nearest available Public Safety Answering Point
(PSAP) based on the call's originating location. Third, the emergency
call service should notify the appropriate emergency response agency as
quickly as possible so it can respond to the emergency.

[0004]While citizens reporting emergency situations could telephone a
police or fire station directly through its individual local telephone
number, it is more effective to provide citizens with a universal, short,
easy to remember number that can be quickly dialed and directly connects
to the nearest PSAP automatically. Most emergency call services in the
U.S. and Canada utilize 911 as the short three digit emergency telephone
number that automatically reaches a PSAP. As of 2006, 99 percent of the
U.S. population had access to 911 services. Other countries have
implemented the same or similar emergency call services for their
citizenry. For example, the European Union has established 112 as the
universal emergency number for all its member states. In most E.U.
countries, 112 is already implemented and can be called toll-free from
any telephone or any cellular telephone. For purposes of simplicity,
emergency call service will be referred to herein as a 911 system.

[0005]Typically, there is no national 911 system. Rather, the answering
points and corresponding dispatch services are locally established and
maintained. In many locations in the U.S., for example, the 911 service
is a joint effort between local governments and all phone companies
active in the area. The cost of a 911 system is paid through local taxes
and through a surcharge on the local citizenry's phone bill. Typically,
the PSAP and corresponding emergency services are set up and maintained
locally, usually by county, often in a joint effort between local
government and any phone company active in the area. Once an emergency
call is connected to the local PSAP, the appropriate local emergency
services may be dispatched for fast response.

[0006]Within the conventional Public Switched Telephone Network (PSTN)
system, emergency 911 calls are made through standard land line
telephones operating on the PSTN. Because telephones in a conventional
PSTN are stationary, various capabilities of a basic 911 system may be
easily enabled. For example, Automatic Number Identification (ANI) may be
implemented. As its name suggests, ANI automatically identifies the
telephone number of the calling party. Coupled with Automatic Location
Identification (ALI), the 911 system can automatically identify both the
source and location of the calling telephone station. In this way, the
location of the emergency situation may be determined without any verbal
communication from the party making the 911 call. This is beneficial
because in many times in emergency situations, callers are panicked or
hurt and cannot verbally communicate the location or nature of the
emergency. In addition, by automatically knowing the caller's location
information, the 911 system may route the call to the nearest PSAP so as
to dispatch the closest emergency response services to achieve the
fastest response.

[0007]In addition, many phone companies and public safety agencies have
collaborated to create Master Street Address Guides (MSAG) which are
master maps that can match phone numbers, addresses and cross streets to
their corresponding PSAP. When an emergency call is made, the 911 system
network hub may use the MSAG to provide emergency response services with
the fastest route to respond to the caller's location.

[0008]FIG. 1A illustrates the handling of a basic conventional 911 call.
In a basic conventional 911 system, a caller 101 dials 9-1-1 (or the
assigned emergency number). The PSTN switch automatically recognizes the
911 number and routes the call to a dedicated 9-1-1 switch 102 that sends
the call to the designated PSAP 103 for the PSTN switch that first
received the call.

[0009]The PSAP call-taker (also called an operator or dispatcher) asks
what the emergency is, what the location is and for a call-back phone
number. Depending on the emergency, the call-taker uses radio dispatch to
alert police, fire and/or EMS to go to the scene.

[0010]FIG. 1B illustrates the handling of an enhanced conventional 911
call. In the enhanced 911 system, a caller 101 dials 911 (or the assigned
emergency number). The PSTN switch recognizes the 911 number dialed and
accesses the ANI to get the number of the station initiating the call and
routes the call to the dedicated 9-1-1 switch 102 that acts as a hub for
the local network. The network uses the telephone number of the
initiating telephone station to get the address from the ALI and uses the
address to determine the proper PSAP 103 destination from the MSAG 104
(this is sometimes called selective routing, because the switch uses
dynamic data to determine where to send the 911 call instead of blindly
routing it to a pre-determined PSAP). In most cases, this all takes a
little over one second. The 911 call now carries the initiating call
station phone number and address along with the caller's 101 voice data
to the nearest available PSAP 103. This information is displayed on the
call-taker's computer when he or she takes the 911 call.

[0011]Some PSAPs 103 simultaneously send the ANI/ALI data to the police
computer dispatch network to allow for immediate access. If necessary,
many PSAPs can transfer the call and its accompanying data to another
PSAP.

[0012]While the 911 system is extremely effective when calls are initiated
on conventional PSTN telephones, mobile device (e.g., cellular
telephones) and Voice over Internet Protocol (VoIP) calls have posed new
problems to 911 systems. For one, mobile devices and VoIP calls do not
provide location information to the system. Thus, 911 calls may not be
routed to the nearest PSAP. As of 2006, more than 8 million people in the
United States use a mobile device as their primary phone. Public-safety
agencies report that wireless calls make up anywhere from 30 to 50
percent of emergency service calls. To accommodate this transformation in
the telephone usage, changes have been implemented in most 911 systems.

[0013]Until recently, when someone called emergency services from a mobile
device, no information appeared on the call-taker's screen, even in
enhanced emergency call service systems. Without this information, the
emergency call wasn't always routed to the PSAP closest to the caller's
location. Consequently, the emergency call could end up at any PSAP in
the remote vicinity, depending on how the individual wireless provider
servicing the particular mobile device had set up emergency call routing.

[0014]To address this problem, Congress has mandated that cellular service
providers configure their systems and the mobile devices that they
support so that the location of a caller can be determined when a 911
call is placed. Local 9-1-1 systems have been implementing changes to
9-1-1 to allow for greater wireless compatibility, and upgrades are still
happening now. A number of methods are used to locate 911 callers. Many
new mobile devices include a Global Positioning System (GPS) receiver
within the mobile device's circuitry. Such mobile devices can provide
location information to the cellular telephone system over a data link.
Cellular systems can also determine the general location of a 911 caller
by triangulating the distance from multiple cell towers to the caller's
mobile device.

[0015]To implement Congress's mandate, the Federal Communications
Commission (FCC) has defined cellular telephone system upgrades to be
accomplished in two phases.

[0016]Phase I provides the call-taker with the ability to see the mobile
device-phone number of the 9-1-1 caller and the location of the
cell-tower antenna with which the mobile device is connected. This phase
also requires that the call be routed to the PSAP nearest to that tower.
As of 2006, 83.6 percent of PSAPs have met all or part of Phase I
requirements. Using the cell-tower location, Phase I technology can only
locate a mobile device within a 3-6 mile radius.

[0017]Phase II provides the call-taker with the ability to see the mobile
device phone number and the location of caller to an accuracy of 50 to
300 meters depending on the type of location system being used by the
wireless provider. This phase also requires that the call be routed to
the PSAP nearest to that location or nearest to the cell antenna in use,
depending on the particulars of the system. As of 2006, 65.2 percent of
PSAPs have met all or part of Phase II requirements.

[0018]There is no standardized method for implementing Phase II
requirements, so wireless providers, in conjunction with local
public-safety agencies, are using various technologies for providing
mobile device location information to PSAPs. There are two basic
approaches: handset-based and network-based.

[0019]FIG. 1c illustrates how a 911 call from a mobile device is connected
to a PSAP. In a handset based embodiment, a GPS receiver built into the
mobile device is utilized. When a caller 101 initiates a 911 call from a
mobile device with a GPS receiver built in, the GPS receiver locates
itself using satellites 110 orbiting overhead. The GPS receiver in the
mobile device receives radio signals emitted by at least three satellites
110, measuring the time it took the signals to reach the receiver. Using
trilateration, the GPS receiver can determines its location coordinates.
The location coordinate information accompanies the voice and phone data
transmitted to the base station. The base station and MTSO 111 either
forwards the call to the dedicated 9-1-1 switch 102 (the same ones used
by landline calls) for PSAP routing or routes the call to the nearest
PSAP, depending on the routing path the wireless carrier chooses. At the
PSAP 103, mapping equipment (typically the CAD equipment discussed in the
previous system) converts the caller's coordinates to a street address
that the call-taker can understand and provide to dispatched emergency
personnel.

[0020]A network -based embodiment is different from the handset-based
embodiment only in how the mobile device generates its latitude and
longitude coordinates. As shown in FIG. 1D, a common implementation of
network-based location-finding involves putting additional radio
equipment on network base stations so that, in essence, they act
something like a GPS receiver for signals received from the mobile
device. When a caller dials 9-1-1 on the mobile device, the mobile device
sends out radio signals to at least three of cell towers 113, and
receivers in each tower times how long it takes for the signal to reach
the tower. Using trilateration, the network can then estimate the
location of the mobile device to within an accuracy of 100 to 300 meters.
Once the network has estimated the latitude and longitude coordinates of
the phone, this information is included with the voice call transmitted
to the network switching station 111 via the base station 112 from which
it is connected.

[0021]While local citizens using their mobile devices may now access
conventional emergency call service systems, large scale emergencies
sometimes destroy or render inoperable conventional emergency call
service systems. For example, large scale emergencies such as natural
disasters (e.g., earthquakes, floods and hurricanes) and terrorist
attacks can disable some or all PSTN telephone and cellular telephone
infrastructure. In such instances, citizens using either wired or
wireless communication devices do not have any access to emergency call
services. Cut off from 911 service, citizens are no longer able to aid
first responders by reporting developments on their cell phones.

SUMMARY

[0022]Various embodiment systems and methods provide wireless emergency
call service to local civilian (i.e., non-emergency personnel) citizens
via a deployable mobile "switch on wheels." In emergency situations where
conventional wireless telecommunications infrastructure is damaged or
inoperable, a mobile switch on wheels may be deployed to the affected
area to provide emergency personnel with wireless telecommunications
capabilities. In order to conserve the limited communications resource
capacity of the mobile switch on wheels, only emergency personnel mobile
devices are programmed with the appropriate system identification number
(SID) needed to access those mobile devices to conduct wireless
telecommunication calls. The various embodiment systems and methods add
wireless emergency call service for the local citizenry by providing the
SID of the mobile switch on wheels to civilian mobile devices in a
secondary preferred roaming list (PRL) which only allows emergency
service calls. The civilian mobile devices may be programmed to search
for SIDs in a secondary PRL after the primary PRL has been exhausted.
Alternative embodiments allow civilian mobile devices to search for SIDs
in the secondary PRL immediately in order to conserve battery power.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]The accompanying drawings, which are incorporated herein and
constitute part of this specification, illustrate exemplary embodiments
of the invention. Together with the general description given above and
the detailed description given below, the drawings serve to explain
features of the invention.

[0029]FIG. 4 is a process flow diagram of an embodiment method suitable
for implementation on a mobile device.

[0030]FIG. 5 is a process flow diagram of an alternative embodiment method
suitable for implementation on a mobile device.

[0031]FIG. 6 is an emergency call system operating on a deployable
wireless base station.

[0032]FIG. 7 is a component block diagram of an example cellular telephone
network gateway suitable for use in the various embodiments.

DETAILED DESCRIPTION

[0033]Various embodiments will be described in detail with reference to
the accompanying drawings. Wherever possible, the same reference numbers
will be used throughout the drawings to refer to the same or like parts.
References made to particular examples and implementations are for
illustrative purposes and are not intended to limit the scope of the
invention or the claims.

[0034]As used herein, the terms "cellular telephone," "cell phone" and
"mobile device" are used interchangeably and refer to any one of various
cellular telephones, personal data assistants (PDA's), palm-top
computers, laptop computers with wireless modems, wireless electronic
mail receivers (e.g., the Blackberry® and Treo® devices),
multimedia Internet enabled cellular telephones (e.g., the iPhone®),
and similar personal electronic devices. A mobile device may include a
programmable processor and memory as described in more detail below with
reference to FIG. 6. In a preferred embodiment, the mobile device is a
cellular handheld device (e.g., a cellphone), which can communicate via a
cellular telephone network.

[0035]Ironically, one of the biggest problems of the 911 emergency call
system is its vulnerability to large scale emergency situations in which
the 911 emergency call system would be needed most. In response to a
disaster situation, one of the highest priorities is to enable
communications. Without effective communications emergency resources
cannot be effectively mobilized. In many disaster situations,
conventional communication infrastructure may be destroyed, damaged or
rendered inoperable. When an emergency situation destroys or renders
inoperable PSTN equipment and cellular towers, all forms of
communications, including emergency call services, may be impossible.

[0036]To provide emergency response teams and personnel with the ability
to communicate in such situations, deployable cellular communication
antennas have been developed. Such deployable units, referred to herein
as a "switch on wheels," can include any wireless base station such as
CDMA2000/EVDO, WCDMA, LTE, IS-136, GSM, WiMax, WiFi, AMPS, DECT,
TD-SCDMA, or TD-CDMA and switch, Land Mobile Radio (LMR) interoperability
equipment, a satellite Fixed Service Satellite (FSS) for remote
interconnection to the Internet and PSTN, and, optionally, a source or
remote electrical power such as a gasoline or diesel powered generator. A
more complete description of an example deployable switch on wheels is
provided in U.S. patent application Ser. No. 12/249,143, filed Oct. 10,
2008, which claims the benefit of priority to U.S. Provisional
Application No. 60/979,645 filed Oct. 11, 2007, the entire contents of
which are hereby incorporated by reference in their entirety.

[0037]A deployable switch on wheels provides first responders with a
portal to the conventional communications infrastructure outside the
emergency location that remains unaffected by the emergency. Much like a
mobile cellular antenna tower, the switch on wheels provides first
responders with the ability to utilize their conventional cellular
telephones even when the conventional stationary cellular tower antennas
have been destroyed. The deployable switch on wheels includes a mobile
cellular antenna that can be deployed to act as a temporary cellular
tower antenna. The deployable switch on wheels may have a broadcast range
approximating that of a conventional cellular tower antenna. The switch
on wheels sends and receives communication signals from a plurality of
mobile devices and serves as a gateway portal to the rest of the
conventional communications infrastructure. When a communication signal
is received by the switch on wheels from one of the plurality of mobile
devices, the communication signal may be broken down into packets for
transport as a voice-over-Internet-protocol (VoIP) communication. The
VoIP communication signal can be transmitted via a satellite owned by a
satellite service provider to a ground station far from the emergency
where the communication can be forwarded through the Internet to the
intended call recipient's telephone number. When a call is made to one of
the plurality of mobile devices utilizing the switch on wheels as its
local base station, the call is routed to the satellite service
provider's router from which the call is sent via satellite relay to the
switch on wheels where the call is ultimately forwarded to the intended
mobile device.

[0038]Depending on the magnitude of the disaster situation, multiple
switch on wheels may be deployed to the disaster area. Deploying multiple
switch on wheels within a region creates an ad hoc wireless communication
network which provides first responders with adequate network coverage to
effectively utilize their cellular telephones until the cellular
telephone infrastructure can be returned to service. In long term
disaster situations, such as may occur when a coastal region is affected
by a major hurricane, the switch on wheels network may remain in place
for an extended period of time until conventional communications
infrastructure can be repaired or replaced.

[0039]While a switch on wheels provides considerable communication
infrastructure to first responders whose cell phones have been programmed
to communicate with the switch on wheels, it would be advantageous to
enable local citizens to access the switch on wheels for emergency
911-type calls. This capability would allow citizens to report ongoing
and developing emergency situations occurring within the disaster area.
By enabling the local citizenry to assist in this manner, fewer first
responder personnel are needed to patrol for new or developing emergency
situations, enabling those first responders on scene to focus on the
emergency at hand.

[0040]Special provisions must be taken to provide civilian citizens with
access to an ad hoc network established by the switch on wheels. Some
types of cellular phones, such as those using GSM technology, will
recognize an unknown GSM network (switch on wheels network) at least for
the purposes of minimal communication, such as placing 911 calls. If the
switch on wheels is maintaining a GSM network, civilian GSM phones will
be able to connect to it for purposes of dialing 911. However, cellular
phones using the CDMA technology will not recognize an unknown network,
such as an ad hoc network provided by the switch on wheels. Unless this
limitation is addressed, citizens owning CDMA cell phones may not be able
to place 911 calls via an ad hoc network provided by the switch on
wheels.

[0041]On the other hand, granting civilians unfettered access to the
switch on wheels could overburden the limited capacity of the switch with
non-essential calls, potentially blocking access by first responders. Due
to the limited number of switches on wheels that may be deployed in an
affected area and their limited capacity, bandwidth for communication
channels is limited in an ad hoc network. Such bandwidth must be reserved
for communications among first responders and emergency service personnel
for command and control purposes. Thus, access by the general public must
be limited to emergency 911-type calls. In other words, civilian
communications must be limited to emergency 911-type calls only, and
perhaps in some instances, the receipt of calls from authorized emergency
personnel.

[0042]Beyond the problems of providing access and managing bandwidth
capacity, there is the challenge of routing 911 calls to the appropriate
PSAP. In a typical deployment, the switch on wheels routes calls destined
for recipients beyond its communication radius via satellite to a ground
station that may be a thousand miles or more away. Thus, 911 calls need
to be routed back through whatever communication network remains to a 911
call center supporting the location of the caller. Since the deployable
switch on wheels is, by its very nature, mobile and not associated with a
permanent location, there needs to be a way of routing a 911 call to the
appropriate PSAP that will be able to assist the caller. Also, a natural
or manmade disaster that requires deployment of a switch on wheels may
also destroy or render inoperable the nearest PSAP, so there may be a
need to route 911 calls to a backup or temporary PSAP.

[0043]Conventional cellular telephones and other mobile communication
devices are assigned special codes that are used in establishing and
routing calls. These codes are used to identify the individual phone, the
phone's owner (or at least the owner's service contract number) and the
contracted service provider. These codes include:

[0044](a) an Electronic Serial Number (ESN), which is a unique 32-bit
number programmed into the mobile device when it is manufactured;

[0045](b) a Mobile Identification Number (MIN), which is a 10-digit number
derived from the unique phone number assigned to the mobile device;

[0046](c) a System Identification Code (SID), which is a unique 5-digit
number that is assigned to each wireless service provider by the FCC; and

[0047](d) a Preferred Roaming List (PRL) for CDMA-type mobile
devices/Public Land Mobile Network (PLMN) for GSM-type mobile devices,
which are prioritized listings of approved SID's that the wireless
provider provides to the mobile devices in order enable mobile devices to
determine network SIDs that the mobile device is allowed to utilize for
service.

[0048]While the ESN is considered a permanent part of the mobile device,
the MIN, SID and PRL/PLMN are programmed into the mobile device when a
wireless service plan is purchased and the mobile device is activated.
The purchased wireless service plan is provided by a particular wireless
service provider which is referred to as the "home system." The
programming of these codes is typically done by the selected wireless
service provider in a process that is sometimes referred to as
"provisioning."

[0049]As part of the provisioning process, CDMA-type mobile devices are
programmed with a PRL, while GSM-type mobile devices are provisioned with
a PLMN which operates similar to the PRL. For simplicity, the embodiments
are described using CDMA terminology. One of skill in the art would
appreciate that similar embodiment systems and methods may be implemented
with GSM-type mobile devices by modifying the PLMN in the same manner as
the PRL modifications described below. The Telecommunications Industry
Association/Electronics Industry Association Interim Standard 683A
(TIA/EIA/IS-683A), which is hereby incorporated herein by reference in
its entirety, provides for a Preferred Roaming List (PRL) for Code
Division Multiple Access (CDMA) mobile communications systems such as
cellular telephones.

[0050]A mobile device's system acquisition function uses information
contained in the PRL to determine the order in which listed analog
frequencies or channels will be tried when the mobile device must acquire
a wireless network system (also referred to as a network or communication
network). A mobile device will attempt to acquire network access (i.e.,
locate a channel or frequency with which it can access a wireless
network) at initial power-on or when a current channel or frequency is
lost for a variety of possible reasons.

[0051]When the user of a mobile device travels beyond the geographic of
the user's service provider network, the mobile device must locate a
another communication network that will provide it with wireless
services. The mobile device's PRL lists communication networks that the
mobile device is authorized to access. Associated with each communication
network in the PRL is a system ID (SID), as well as corresponding
acquisition parameters (frequency band, channel, etc.) for each
communication network. The PRL is created, loaded and updated by the
user's service provider.

[0052]The PRL is maintained in such a manner that the mobile device can
readily determine which communication networks cover common geographical
regions. The references to common geographic regions refers to areas of
common radio coverage. Moreover, the communication networks that cover a
common geographical region are prioritized, i.e., ranked from most
desirable to least desirable. The mobile device is programmed to attempt
to acquire service starting with the highest priority communication
network in the mobile device's current geographical area. There is no
point in trying to acquire service on a communication network outside of
the mobile device's current geographic region, since communication
networks typically provide service only within a limited geographic
region.

[0053]Many wireless service providers recommend that users regularly
update the PRL on their mobile devices if they use their phones outside
the home system frequently, particularly if they do so in multiple
different areas. Updating the PRL allows the mobile device to choose the
best roaming carriers, particularly "roaming partners" with whom the
user's service provider has cost-saving roaming agreements, rather than
use non-affiliated carriers. PRL files can also be used to identify the
home network system along with roaming partners, thus making the PRL an
actual list of the total coverage available to the user, including both
home and roaming coverage.

[0054]The PRL is maintained by the wireless service provider operator and
is normally not accessible to the user. Many wireless service providers
allow users to download the latest PRL to their device by dialing an
Over-The-Air (OTA) feature code, such as *228. Alternatively, the latest
PRL may be downloaded into the mobile device via a hardwire connection.

[0055]The PRL consists of two tables (along with some header and overhead
information). The two tables include a System Table and an Acquisition
Table. The System Table is a prioritized list of communication networks
that the mobile device is permitted to access (home system and roaming
networks). Each communication network entry in the system table belongs
to a geographic area known as a GEO. These GEOs are listed in priority
order. Thus, as a mobile device enters different GEOs, the priority order
in which roaming networks are to be searched may alter. Each entry also
provides an acquisition table index where the frequencies associated with
that particular communication network are identified and a roaming
indicator that dictates the type of indication (e.g., "roaming") which
should be displayed to the user when they are receiving service from that
network. The Acquisition Table is an indexed list of frequencies on which
the mobile device may search for particular networks. The idea behind the
acquisition table is to optimize the acquisition time by identifying only
the frequencies that should be searched, rather than forcing the mobile
device to search the entire frequency spectrum.

[0056]FIG. 2 illustrates an exemplary prior art system table and
acquisition table for a PRL for a particular geographic region. The
Acquisition Table 152 in FIG. 2 contains records that list communication
channels or frequencies in a priority contact order from top to bottom.
For the Acquisition Table shown, for example, a mobile device would
contact PCS CDMA Block B channels first, followed by Block A channels,
and then channels 283, 699, 384, and 777. If the mobile device cannot
contact these CDMA channels, the mobile unit would attempt contact with
Cellular Analog System A frequencies.

[0057]The PRL's System Table 151 contains records having several fields.
The "SID" field contains the System Identification number of preferred
communication networks. The "selection preference" identifies the
relative priority of each network in terms of connection desirability. As
shown, for example, it is most desirable for the mobile device to connect
with the home system SID. The "Roaming Indicator" field indicates a
roaming indication display status on the mobile device as either "off" or
"on" depending on which network the mobile device is connected to.
Typically, if the mobile device is connected to its home system, then the
roaming indicator will be off. The "Acquisition Index" field refers back
to the Acquisition Table record number associated with an SID. Thus, the
"Acquisition Index" field entry indicates the channel(s) or
frequency(ies) associated with the particular SID. As shown, for example,
the SID of the home system (Acquisition Index 0) is associated with PCS
CDMA Block B channels (Acquisition Table record 0). Similarly, SID of
Roaming Partner 3 (Acquisition Index 3) is associated with Cellular
Analog System frequencies.

[0058]A typical mobile device processor executes a system acquisition
function to contact a wireless communication network based on PRL
entries. While many variations are possible, the following description
applies to a conventional system acquisition procedure.

[0059]When the mobile device seeks to establish connection to the home
system, the acquisition index will direct the mobile device to search for
a communication channel on the PCS CDMA Block B channels. When the mobile
device encounters a pilot signal from a base station on the PCS CDMA
Block B channels, the system acquisition function continues to operate
and receives an SID from the base station over an associated
synchronization channel. The acquisition function then compares the
received SID to the SIDs in the PRL system table 151. If the received SID
matches the SID of the home system, then the mobile device will establish
a communication connection with the home system. If the SID carried on
the associated synchronization channel does not match the SID listed in
the system table 151, the mobile device will behave as if it never
received a signal on the scanned frequency.

[0060]If after scanning the PCS CDMA Block B channels the SID of the home
system is not found, the mobile device will then attempt to establish
connection with the next priority network listed in the system table 151.
In the illustrated example the mobile device will seek out "Roaming
Partner 1." Accordingly, the mobile device will search for a
communication channel on the PCS CDMA Block A channels. When the mobile
device encounters a pilot signal from a base station on the PCS CDMA
Block A channels, the system acquisition function continues to operate
and receives a SID from the base station over an associated
synchronization channel. The acquisition function then compares the
received SID to the SIDs in the PRL system table 151. If the received SID
matches the SID of Roaming Partner 1, then the mobile device will
establish a communication connection with Roaming Partner 1's network. If
the SID carried on the associated synchronization channel does not match
the SID listed in the system table of Roaming Partner 1, the mobile
device will then seek out the next priority network listed in the system
table 151. This process will continue until the mobile device connects to
a network or the list of authorized networks in system table 151 is
exhausted. If the mobile device exhausts all of the authorized networks
listed in the system table 151, the mobile device concludes that no
service is available and may post the "No Service" message on its
display.

[0061]In order to limit access to the switch on wheels, the SID of the
switch on wheels is not released to any non-authorized mobile device.
Thus, the SID of the switch on wheels does not exist in the PRL of
civilian CDMA mobile devices. Consequently, no unauthorized mobile device
(i.e., a mobile device belonging to civilians) can establish connection
to the switch on wheels. To provide civilians with emergency 911 access
the switch on wheels communications resources, an embodiment modifies the
provisioning of mobile devices to include a secondary PRL in addition to
the primary PRL described above. The modified provisioning may occur when
a mobile device is first provisioned or during subsequent provisioning
updates which may be performed using wired or OTA provisioning methods.

[0062]FIG. 3 illustrates the primary and secondary PRLs of an embodiment
that provides switch on wheels emergency call service access to the
mobile devices of the local citizenry. In this embodiment, mobile devices
may be provisioned with a primary PRL as well as a secondary PRL. The
primary PRL may include a primary system table 161 and a primary
acquisition table 162. The secondary PRL may include a secondary system
table 163 and a secondary acquisition table 164. The primary PRL system
table 161 is similar to the conventional PRL system table 151 described
above with reference to FIG. 2, except that it is modified to include a
column (i.e., a data field within each data record) containing a flag
which for purposes of this description is entitled
"Switch-to-secondary-PRL flag." The purpose of the
switch-to-secondary-PRL flag is to inform the mobile device whether it
should initiate the use of the secondary PRL. As the mobile device
progresses through the system acquisition process described above, the
mobile device may reach an entry in the system table 161 that has the
switch-to-secondary-PRL flag set. In the example shown in FIG. 3, the
network entry "Roaming Partner 3 has the switch-to-secondary-PRL flag
set. If the mobile device has not established communication with a
network by the time the mobile device encounters a data record in the
primary PRL system table 161 which has the switch-to-secondary-PRL flag
set (e.g., storing a value of "1"), the mobile device will initiate an
emergency call service subroutine. The emergency call service subroutine
places the mobile device in an emergency mode and only allows the mobile
device to place emergency calls (e.g., 911 type calls). In this mode the
mobile device will access the secondary PRL and scan for available
emergency networks which may include the switch on wheels. Thus, in the
example shown in FIG. 3, if the mobile device is unable to establish
communications with any network after seeking out Roaming Partner 3, the
mobile device will initiate the emergency call subroutine and seek a
communication network from the networks listed in the secondary system
table 163 of the secondary PRL.

[0063]FIG. 4 illustrates the process flow of an embodiment method that
provides switch on wheels emergency call service access to civilian
mobile devices. As the mobile device performs its main loop 201 routine a
variety of circumstances may require the mobile device to attempt to
acquire a new communication network. For example, as the mobile device
travels it may move out of range of the network with which it is
currently communicating. Thus, the mobile device routinely checks to
determine if a new communication network is needed, step 202. If a base
station is available with sufficient signal strength within the
communication network to which the mobile device is currently connected
then the mobile device does not need to find a new network (i.e., step
202="No") so the mobile device continues with main loop routine 201. If,
however, the mobile device determines that a new communication network is
needed (i.e., step 202="Yes"), the processor of the mobile device will
access the SID and communication parameters for the highest priority
communication network listed in the primary PRL system table 161, step
203. In instances where the mobile device seeks out a new communication
network due to power up, the home system will be the highest priority
network. The mobile device processor scans the listed frequency and
channel for the selected network by using the acquisition index
corresponding to the selected network and acquisition table 162, step
204. If the mobile device encounters a pilot signal on the scanned
frequency, step 205, the system acquisition function receives an SID from
the base station over the associated synchronization channel. The
received SID is compared with the SID stored in the system table 161 to
determine if the selected network channel is found, step 205a. If the
received SID matches the expected SID listed in the system table 161
(i.e., step 205a="Yes"), then the mobile device sets up the communication
channel with the communication network and allows the mobile device to
conduct communication as normal, step 206. It is noted that the steps of
checking for a pilot signal, step 205, and comparing the SID to the
expected SID, step 205a, may be accomplished in a single step.

[0064]If the no pilot signal is obtained on the designated frequency
(i.e., step 205="No") or if the received SID does not match the expected
SID for the selected network in the system table 161 (i.e., step
205a="No"), then the mobile device processor will check the system table
161 to determine if the switch-to-secondary-PRL flag has been set, step
207. Referring to the exemplary system table 161 in FIG. 3, the
switch-to-secondary-PRL flag is not encountered as set until the mobile
device processor has attempted to connect with Roaming Partner 3. If the
switch-to-secondary-PRL flag has not been set (i.e., step 207="No"), then
the mobile device processor will determine if any more networks appear in
the primary PRL system table 161, step 214. Referring back to the system
table 161 of FIG. 3, three additional networks may be selected. Thus, as
long as additional communication networks are listed in the primary PRL
system table 161 (i.e., step 214="Yes"), the mobile device will continue
to scan for available networks in the primary PRL to connect through by
returning to select the next highest priority network from the primary
PRL, step 203. If no additional networks are available (i.e., step
214="No"), then the mobile device will have exhausted all available
networks without being able to connect with any. Accordingly, the mobile
device will indicate that "No Service" is available, step 213, after
which processing may return to the main loop 201.

[0065]If, however, the mobile device scans each of the available networks
in the primary PRL and discovers a record in which the
switch-to-secondary-PRL flag is set (i.e., step 207="Yes"), the mobile
device processor will initiate the emergency call sub-routine and select
the highest priority networks listed in the secondary PRL system table
163, step 208. For example, referring to the primary and secondary PRLs
shown in FIG. 3, if the mobile device scans for Roaming Partner 3, but
still is unable to find or connect with any of the listed networks in the
primary PRL system table 161, the switch-to-secondary-PRL flag set in the
Roaming Partner 3 data record of the primary PRL system table 161 will
cause the mobile device processor to refer to the secondary PRL's system
table 163. Similar to the primary PRL system table 161, the secondary PRL
system table 163 is a prioritized list of emergency networks that the
mobile device is permitted to access. Referring to the exemplary
secondary PRL system table 163, the SID of the switch on wheels is
listed. While the exemplary secondary PRL system table 163 shown in FIG.
3 only lists a single emergency network, as with the primary PRL system
table 161, multiple emergency networks may be listed in the secondary PRL
system table.

[0066]Using the communication parameters listed for the highest priority
network in the secondary PRL system table 163the mobile device scans the
corresponding frequency or channel, step 209. For example, FIG. 3 shows
that the emergency switch on wheels network listed in the secondary PRL
system table 163 communicates on the PCS CDMA Block B channels. The
mobile device determines whether a pilot signal is present on the scanned
frequency compares any received SID to the SID stored in the secondary
PRL system table 163 to determine if the selected network channel is
found, step 210. If a pilot signal is encountered and the received SID
matches the expected SID listed in the secondary PRL system table 163
(i.e., step 210="Yes"), then the mobile device sets up an emergency
communication channel with the selected emergency communication network
and configures the mobile device to complete only emergency calls (e.g.,
911-type calls), step 211. In setting up the emergency communication
capability, the mobile device will be programmed to allow the user to
place calls that are dialed to a recognized an emergency call service,
such as 911. Calls to other numbers (i.e., other than 911, for example)
will not be executed (i.e., there will be no attempt to place the call
through the connected network).

[0067]In alternative embodiments, the emergency communication channel may
be configured to also allow the user to receive calls over the switch on
wheels from emergency services only. In this manner emergency services
may contact the user to obtain additional information regarding the
emergency that is being reported. This capability will maximize the
limited resources associated with the radio access network as well as the
backhaul to the PSAP during time of crisis. Such capability can be
implemented at the switch on wheels which can be configured to route
calls to civilian mobile devices only if they originate at a recognized
and authorized first responder. The mobile device may be configured to
receive any calls directed to it from the connected communication
network.

[0068]If no pilot signal was encountered on the selected frequency or
channel or if the received SID does not match the expected SID for the
selected emergency network in the secondary PRL system table 163 (i.e.,
step 210="No"), the mobile device processor will check the secondary PRL
system table 163 to determine if any more emergency networks appear in
the secondary PRL system table 163, step 212. If no additional emergency
networks are available (i.e., step 212="No"), then the mobile device will
have exhausted all available emergency networks without being able to
connect with any, so the mobile device will indicate that "No Service" is
available, step 213. Having found no available communication networks,
emergency or otherwise, the mobile device returns to the main loop 201
until the next search for a new network is initiated.

[0069]In an alternative embodiment, optional steps illustrated in FIG. 5
may be included to place the mobile device in a standby mode for a
pre-determined period of time after determining that no service is
available, step 214. Once the pre-determined period of time has elapsed,
the mobile device may initiate another search for a new network by
returning to step 203. In this manner, the mobile device may conserve
additional battery resources by preventing the mobile device from
continually searching for networks when it determines that no service is
available. This embodiment helps to ensure that mobile device batteries
are not rapidly depleted searching in vain for network services in
disaster situations in which communications infrastructure is destroyed
or rendered inoperable. Often the same event that knocks out cellular
communication infrastructure will affect the electrical power
infrastructure as well. By restricting the frequency of network searches,
mobile device battery stores can be preserved until communication
infrastructure is restored or a switch on wheels is put in place. Thus,
this embodiment ensures that civilian mobile devices remain available
when emergency communication networks are activated even when electrical
utilities are not available.

[0070]Referring to FIG. 5, the embodiment method may proceed as described
above with reference to FIG. 4 with the addition of a few steps. For
example, before initiating a search for a new network, the processor may
check a count down timer included to provide the time delay described
above, step 219. If the counter equals zero (i.e., step 219="Yes"), the
process of searching for a new network described above with reference to
FIG. 4 will proceed through like numbered steps. If the counter does not
equal zero (i.e., step 219="Yes"), this indicates that a delay is
implemented, so the counter may be decremented, step 221, before the
process returns to the main loop 201.

[0071]The amount of delay between searches for new networks can be
controlled by adjusting the setting of the counter tested in step 219.
For example, if the process determines that no service is available
without checking the secondary PRL (i.e., step 214="No"), the counter may
be set to a short pause value, step 215, as may be appropriate when the
mobile device has not been programmed with a secondary PRL. In such
situations, which may reflect the ordinary course, the mobile device may
be temporarily in a location of no service, such as in a building, with
no emergency situation occurring so a short delay before the next network
search is appropriate. However, if the process determines that no service
is available after checking all networks listed in the secondary PRL
(i.e., step 212="No"), the counter may be set to a long pause value, step
217. In such situations, which may reflect an emergency situation, the
mobile device has been programmed to search for emergency networks, and
presume that there may be a significant delay before a network becomes
available making it appropriate to implement a longer delay.

[0072]In another alternative embodiment, the secondary PRL acquisition
table 163 may be omitted. Because the frequency at which the emergency
networks operate may be the same as other non-emergency networks, an
alternative embodiment may employ a single acquisition table. In the
alternative embodiment, the secondary PRL may comprise a secondary PRL
system table 162 which includes an acquisition index that refers to the
various network frequencies and channels listed in the primary PRL
acquisition table 162.

[0073]In some situations the disaster event may be predictable. For
example, meteorologists can accurately predict major weather events such
as tornados, hurricanes or other major storm systems that may destroy or
render inoperable communications infrastructure. In order to pro-actively
respond to such situations, emergency services may preemptively deploy
equipment near the area expected to be affected. Cellular network service
providers can then send out an OTA update to the PRL adding in the
secondary PRL and setting the appropriate flags in the primary PRL.
Alternatively, civilian mobile devices may be provisioned with a primary
and secondary PRL but without the switch-to-secondary-PRL flag s set. In
this implementation, the OTA update to the PRL may simply set the
switch-to-secondary-PRL flag s allowing the OTA update to be short. For
example, referring to FIG. 3, in order to initiate the scan for the
switch on wheels emergency communication network, the mobile device must
first scan four non-emergency communication networks. In practice, a
mobile device's PRL may contain hundreds of authorized networks listed in
the system table 161. If a major disruptive event is predicted for a
particular area or geo, emergency service officials may ask cellular
service providers to update the provisioning of all mobile devices in the
geographic region so that the switch-to-secondary-PRL flag is set either
immediately or after a small number of commercial networks are scanned in
the particular area or geo. By proactively updating the provisioning of
civilian mobile devices, access to the emergency call service may be more
efficiently enabled. Once the disaster situation has been alleviated, a
new provisioning update may transmitted OTA to return the
switch-to-secondary-PRL flag settings to their values in the primary PRL
system table 161. Even in unpredictable disasters, such as terrorist
attacks and earthquakes, PRL updates may be sent out OTA to all mobile
devices with service and within a particular radius of the affected area.
In this manner, civilian mobile devices which may travel into the
affected area will have emergency 911 service available. Also, mobile
devices may be provisioned outside the area and then distributed to
civilians within the affected area to give them emergency 911 service
until normal cellular service is restored.

[0074]In addition to limiting civilian access to emergency 911 services,
the switch on wheels may also limit access to network resources based on
a tiered priority access system. In such systems the switch on wheels may
include a database of known mobile device EINs, MINs and SIDs which
identify mobile devices in a hierarchy based upon the roles and
responsibilities of the owner and grant access to network resources based
on their relative position in the hierarchy. A more complete description
of an example tiered priority access system is provided in U.S. patent
application Ser. No. 12/273,146, filed Nov. 18, 2008, which claims the
benefit of priority to U.S. Provisional Application No. 60/990,938 filed
Nov. 29, 2007, the entire contents of which are hereby incorporated by
reference in their entirety.

[0075]After access to the communication channels on the switch on wheels
is granted to the local citizenry for emergency service calls, the switch
on wheels must route the emergency calls to the appropriate PSAP where
emergency services can be dispatched. To route the 911 calls to the
nearest appropriate PSAP, the system must first determine the approximate
location from which the call is initiated. Since calls entering the
system will be initiated from wireless mobile devices, the location of
the mobile device must first be ascertained.

[0076]In an embodiment, the switch on wheels may utilize geodetic
information provided by both the network and mobile devices to determine
the location of the caller (and thus the PSAP to which the call should be
routed). In a first embodiment, mobile devices equipped with GPS
receivers can report their location to the switch on wheels in the manner
provided for in conventional cellular telephone networks. In a second
embodiment, the location of the switch on wheels may be utilized as an
approximation of the geographic coordinates of the caller.

[0077]Using the geographic coordinate information provided by the mobile
device's GPS receiver, a server located at the ground station connected
to the switch on wheels via satellite link may determine the appropriate
PSAP to receive the incoming call using a database of PSAP coverage
areas. By maintaining a current database of PSAP geographic assignments,
the ground station can route the call to the proper PSAP as some PSAPs
are shutdown, realigned or otherwise adjusted to deal with the emergency
situation. Using the PSAP information from the database, the receiving
ground station can route the emergency call to the PSAP handling the
region using the PSTN or whatever communication link is established with
the PSAP. It is noted that in some emergencies, the PSAP assigned to
handle the call may be geographically remote, such as in a regional,
state or national emergency control center. Since the call is transmitted
from the switch on wheels is a VoIP communication, the call can be routed
to the selected PSAP over the Internet using VoIP protocols and
equipment.

[0078]FIG. 6 illustrates the emergency call system operating on a
deployable switch on wheels. As shown in the FIG. 5, a plurality of
conventional mobile devices 301a-301d are within communication range of
the deployable switch on wheels 302. Mobile device 301a is a GSM mobile
device distributed to an authorized first responder/emergency personnel.
Mobile device 301b is a CMDA-type mobile device distributed to an
authorized first responder/emergency personnel. Mobile device 301c is a
GSM type mobile device owned by a civilian. Mobile device 301d is a
CDMA-type mobile device owned by a civilian.

[0079]As first responders/emergency personnel members, mobile devices 301a
and 301b are provisioned with the SID of the switch on wheels network
302, so the SID will appear in the primary PRL system table 161 of these
authorized mobile devices. In this embodiment, both mobile devices 301a
and 301b will be able to send and receive voice and data signals to and
from the switch on wheels network. Consequently, if an emergency
situation develops and the switch on wheels is deployed, mobile devices
301a and 301b will be able to interoperate with the switch on wheels 302
in a roaming mode. In this manner, the first responder/emergency
personnel who own and operate mobile devices 201a and 301b will be
provided with full communication capabilities in an emergency situation
where a switch on wheels 302 has been deployed.

[0080]In contrast, mobile devices 301c and 301d are owned by civilians and
so will not have the SID of the switch on wheels included in their
provisioning data. While it is desirable to provide the local civilians
with emergency (e.g. 911) calling capability, it would be undesirable to
provide them with unfettered access to the limited communication
resources of a switch on wheels 302 network. In emergency situations it
is critical to reserve limited communication resources to essential
emergency response communication so that the emergency situation can be
properly managed. Thus, not including the switch on wheels SID in
civilian mobile device 301c and 301d provisioning helps to reserve
emergency communications resources for designated first responders.
Mobile device 301c is a GSM-type mobile device. As such, mobile device
301c will be permitted to initiate an emergency call via the switch on
wheels 302 network as part of standard GSM protocols. Because mobile
device 301c does not contain the necessary SID programmed into its
primary PLMN stored in memory, mobile device 301c will not be able to
receive any voice or data signal from the switch on wheels 302 network.
In addition, for the same reason, mobile device 301c will not be able to
initiate any call other than an emergency call through the switch on
wheels 302 network.

[0081]Mobile device 301d is a civilian CDMA-type mobile device, and as
such will be permitted to initiate an emergency call via the switch on
wheels 302 network only if the SID of the switch on wheels 202 network is
programmed in the secondary PRL system table 163 in its memory. The
switch on wheels 302 network SID may be programmed into the secondary PRL
system table 163 of mobile device 301d by the wireless service provider
when the phone was initially activated or subsequently through a hard
update or an OTA provisioning. Because the switch on wheels 302 network
SID is stored in the secondary PRL system table 163, the mobile device
301d will only access the network in the emergency access mode, and
therefore will not be able to receive any voice or data signal from the
switch on wheels 302 network. In addition, for the same reason, mobile
device 301d will not be able to initiate any call other than an emergency
call through the switch on wheels 302 network.

[0082]As shown in FIG. 6, mobile devices 301a-301d with the SID of the
switch on wheels 302 network stored in either a primary PRL system table
161 or secondary PRL system table 163 receive a control signal from the
deployable switch on wheels 302. A GSM 303 and CDMA 304 call router
located within the deployable switch on wheels 302 communicates with the
plurality of mobile devices 301. The communication signals received from
the GSM 303 and CDMA 304 call routers are sent to a VoIP Router 305
located within the deployable switch on wheels 302 to convert the
communication signals into IP packets capable of being transmitted over
the Internet. As part of the communication signals received by the
deployable switch on wheels 302, location coordinates derived from either
handset provided geodetic information or the location of the switch on
wheels, as well as mobile device phone number data, are transmitted with
the communication signal.

[0083]The signals from the VoIP router 305 are sent to a satellite system
router 306, such as an iDirect unit, as IP packets. The satellite routed
IP packets are relayed to the satellite uplink 307 where the IP packets
are transmitted to a geosynchronous communication satellite 308. The IP
packets are relayed by the satellite 308 to a satellite downlink 309 such
as maintained by a satellite service provider. The received IP packets
are received by the satellite router 310 located in the satellite service
provider facility and routed to an Edge Router 311. The Edge Router 311
uses the location information associated with the call to determine the
PSAP assigned to the callers location, and then routes the 911 call as it
would any VoIP call over the Internet 312 or via the PSTN to the selected
PSAP. In an alternative embodiment, the call or information from the call
may first be routed to a call server 313 which is associated with a 911
clearing house facility that maintains the database of PSAP assignments
for the emergency region so the call server 313 can select the
appropriate PSAP 320. The call may be routed with the use of a selective
server using the process currently used for a VoIP call where the VoIP
call is terminated at the S/S and PSTN Gateway 316 enabling an interface
to the PSAP 320 via traditional telephony circuits. The VOC and ALI
information will also be passed to the appropriate PSAP 320 as part of
the call delivery method enabling the call to be routed to the
appropriate PSAP 320 and call handler at the PSAP. Therefore, once the
appropriate PSAP 320 is determined, the call initiated by one of the
plurality of mobile devices is connected to the selected PSAP 320. In
addition to voice data, the PSAP 320 can receive location coordinates
identifying the location of the mobile device 301 as well as the phone
number of the mobile device 301. In this manner, the PSAP 320 is provided
with the approximate location of the emergency situation being reported
as well as the call back number in the event the call is dropped or
interrupted.

[0084]In embodiments where the programming of the mobile device allows for
the receipt of calls from authorized emergency services over the switch
on wheels in an emergency mode, the system can enable a call back to take
place since the call from the switch on wheels to the PSAP is a VoIP call
and the calling number has an ALI associated with it enabling the PSAP
operator to place a call to the citizens handset that dialed 911. The
reverse 911 call involves the deploy able switch on wheels keeping the
citizens mobile number in the Visitor Location Register (VLR) and mapping
the Temporary Line Directory Number (TLDN) associated with the 911
callers MIN to the VoIP number used as the prefix for the VoIP call
delivery to the PSAP.

[0085]Referring to FIG. 7, a mobile device 301 will typically include a
processor 400 coupled to a random access memory 401 and a wireless
transceiver 402 coupled to an antenna 403 for sending and receiving voice
and data calls via a cellular network. Typical mobile devices also
include a rechargeable battery 404 which provides power to the processor
400 and transceiver 402, allowing the unit to be portable. The mobile
device 301 may also include components typically employed in commercial
cell phones, including a display 406, a keyboard 407, a pointing device
408 and a parallel or serial bus connector 409, all coupled to the
processor 400. The mobile devices 301 may also include a mass storage
device 410 coupled to the processor and random access memory 401, which
may contain large amounts of data. The mass storage device 410 or random
access memory may contain the provisioning/programming information for
mobile device 201 operation. The provisioning/programming information may
include PRLs and positive and negative SID lists as described herein.

[0086]Another embodiment utilizes the additional communication channels
maintained by the deployable switch on wheels 302 to transmit emergency
notifications to all conventional mobile devices in the broadcast area.
While the deployable switch on wheels 302 may only receive emergency
calls from mobile device operated by the local civilians, the additional
communication channels maintained by the deployable switch on wheels 302
may be utilized to transmit emergency information messages to the general
population. These emergency notifications may be in the form of broadcast
voice messages or SMS text messages pushed out to all mobile devices in
the broadcast range. Through the use of the secondary PRL system table
163 the mobile device may camp on the control channel of the switch on
wheels emergency network. The mobile device may also receive SMS or
Cellbroadcast messages regardless of whether the device is GSM or CDMA
because the handset will now recognize the deployable SID as being an
authorized emergency network and can now read the control channel.

[0087]The hardware used to implement the forgoing embodiments may be
processing elements and memory elements configured to execute a set of
instructions, wherein the set of instructions are for performing method
steps corresponding to the above methods. Alternatively, some steps or
methods may be performed by circuitry that is specific to a given
function.

[0088]Those of ordinary skill in the art will appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the embodiments disclosed herein may be
implemented as electronic hardware, computer software, or combinations of
both. To clearly illustrate this interchangeability of hardware and
software, various illustrative components, blocks, modules, circuits, and
steps have been described above generally in terms of their
functionality. Whether such functionality is implemented as hardware,
firmware, or software depends upon the particular application and design
constraints imposed on the overall system. Those of ordinary skill in the
art may implement the described functionality in varying ways for each
particular application, but such implementation decisions should not be
interpreted as causing a departure from the scope of the present
invention.

[0089]The steps of a method or algorithm described in connection with the
embodiments disclosed herein may be embodied directly in hardware, in a
software module executed by a processor, or in a combination of the two.
The software module may reside in a processor readable storage medium
and/or processor readable memory both of which may be any of RAM memory,
flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard
disk, a removable disk, a CD-ROM, or any other tangible form of data
storage medium known in the art. Moreover, the processor readable memory
may comprise more than one memory chip, memory internal to the processor
chip, in separate memory chips, and combinations of different types of
memory such as flash memory and RAM memory. References herein to the
memory of a mobile device are intended to encompass any one or all memory
modules within the mobile device without limitation to a particular
configuration, type, or packaging. An exemplary storage medium is coupled
to a processor in the mobile device such that the processor can read
information from, and write information to, the storage medium. In the
alternative, the storage medium may be integral to the processor. The
processor and the storage medium may reside in an ASIC.

[0090]The foregoing description of the various embodiments is provided to
enable any person skilled in the art to make or use the present
invention. Various modifications to these embodiments will be readily
apparent to those skilled in the art, and the generic principles defined
herein may be applied to other embodiments without departing from the
spirit or scope of the invention. Thus, the present invention is not
intended to be limited to the embodiments shown herein, and instead the
claims should be accorded the widest scope consistent with the principles
and novel features disclosed herein.